Characteristics of very fast transient currents in ultra high-voltage power system with Hybrid reactive power compensation

Abstract

Hybrid reactive power compensation (HRPC) consists of a stepped controlled shunt reactor (SCSR) and a series compensation (SC), which will find applications in future ultra high-voltage (UHV) power grids to resolve the problems due to the frequent change of reactive power and bulk power transmission. However, very fast transient currents (VFTCs) are inevitably generated during switching, which would lead to insulation breakdown. In the present work, we first develop the equivalent model for HRPC, following which we deduce the expression of VFTCs in the time domain by using an inverse Laplace transform. The analysis indicates that the amplitude and frequency of VFTCs are both affected by the capacitance of the SCSR and of the SC, as well as the line length, stray capacitance, etc. The oscillating frequency, peak, and amplitude of the main frequency of the VFTCs in the substation can be modified by adjusting the silicon-controlled rectifiers in the SCSR when the disconnecting switch in gas-insulated switchgear is switched on. When the disconnecting switch in the SC is switched on, the VFTC oscillation frequency in SCSR decreases with increasing stray capacitance of SC, but the frequency and peak of the VFTC remains quite large. Increasing the line length between the SC and the SCSR suppresses the VFTC in UHV power systems. These results lay the foundation for developing HRPC methods to suppress VFTCs in UHV substations.

Study on Very Fast Transient Overvoltage Characteristics of Gas-Insulated Switchgear Substation Based on Hybrid Reactive Power Compensation

“…In particular, great progress has been made on VFTO simulation and calculations. For example, references [1][2][3][4][5] studied the characteristics of simulated VFTOs in di erent switching arc models and compared them with the actual measurements of VFTO waveforms in order to verify the rationality of di erent switch arc models. e study makes the calculated results for VFTO simulations more compatible with the actual VFTO characteristics measured and therefore closer to the real situation.…”

Standstill Time-Domain Response Parameter Estimation of the Large Synchronous Condenser in Arbitrary Rotor Position

“…To ensure the stable transmission of power, the converter stations of UHVDC systems need a large amount of reactive power, especially under conditions with more dynamic variation [3]. The lack of dynamic reactive power may threaten the voltage stability of AC bus in converter stations, therefore resulting in a series of serious faults, such as commutation failure, DC bipolar blocking, and so on [4]. Existing widely used reactive power compensation devices, such as static var compensation devices and static synchronous compensators, are difficult to fulfill the demand due to capacity limitations.…”